The present invention relates to a digital recording and reproduction apparatus for video signals and audio signals in the TV broadcasting, or more in particular to a time shift function.
A conventional technique for recording/reproducing the TV broadcast program is a VTR. The tape medium is considered as an inexpensive medium for recording video signals and audio signals. Nevertheless, the tape medium is not suitable for random access for its structure.
For reproducing the program recorded in the VTR, the tape is required to be rewound to the head of the program. Thus, it is difficult to reproduce the video information already recorded, while at the same time recording a program. The program which the user has started to record using a timer or the like cannot be viewed from the head of the program before the program is completely recorded to the last.
With the optical disk, which is superior to the tape in random accessibility, on the other hand, JP-A-6-290538 discloses a method using a CLV (constant linear velocity) scheme most suitable in terms of recording density for recording, while a CAV (constant angular velocity) scheme superior in accessibility is employed for reproduction. In a system for repeating the recording and reproduction alternately, however, the relation of the target rotational speed between the two processes has not been taken into consideration.
JP-A-11-232844 discloses performing recording and reproduction for each track alternately. However, it does not concretely teach any rotational speed control in the recording and reproduction.
Further, JP-A-7-111629 describes a technique for realizing the time shift using a disk-like recording medium. This technique, however, presupposes the use of two pickups and fails to refer to a method of controlling the rotation.
An object of the present invention is to provide a digital recording/reproduction method and apparatus for video and/or audio signals and an optical disk device therefor in which the time shift is easily realized.
According to one aspect of the present invention, there is provided a digital video/audio signal recording/reproduction apparatus comprising:
means for temporarily storing a digital input signal and a digital output signal;
means for reproducing the input signal from the medium and writing it in the temporary storage means for tp period:
a random-access disk-like recording medium having spiral or concentric recording tracks; and
means for reading an input signal from the temporary storage means and recording the input signal in the random-access disk-like recording medium for the period tr (r: real number), where tr is a recording period from the time point with a predetermined period t (t: real number) when the recording is started in the recording medium at a predetermined transmission rate to the time point when the data amount input during the period t is completely recorded, the period t being segmented into the recording time tr (tr: real number) and the reproduction time tp (=txe2x88x92tr);
wherein the recording means and the reproduction means are operated alternately and intermittently, thereby making substantially simultaneous recording and reproduction possible at different positions. In this way, the user can start the reproduction immediately from the head of a program without waiting for the end of recording the program and the time shift of a broadcasting can be easily realized.
The temporary storage means has a recording data buffer area and a reproduction buffer area. In the case where the recording fails due to a disk defect during the alternate intermittent operation, the write operation is continued without switching to the reproduction mode. As a result, the recording process and the reproduction process may both be delayed and the buffer areas may run short. To meet this situation, a part or the whole of reproduction buffer area is replaced with a recording buffer area to prevent the shortage of the recording buffer area. Even when the disk develops a defect, therefore, the recording operation is given priority and successfully continued although the reproduction may be interrupted.
Also, at the time of recording into a disk, the disk motor is controlled at CLV with a predetermined rate, and at the time of switching to the reproduction mode, the rotational speed is held, so that the reproduction is carried out at variable speed corresponding to the reproduction rate changing during the reproduction period. When the reproduction is switched to the recording mode, therefore, the CLV control is rapidly stabilized since the rotational speed is held at the target. Thus, even with a single optical pickup, the intermittent operation of recording and reproduction can be realized with stable recording operation.
Further, a disk specified to record from the inner toward the outer periphery is segmented into a plurality of concentric zones, and the intermittent recording and reproduction operation described above is carried out from inner toward outer periphery within each zone and from outer toward inner peripheral zone in the area between the zones. As a result, the zone from which the recorded data is reproduced is located on the outer peripheral side than the zone being recorded. Thus, the variable reproduction rate is always higher than the fixed recording transmission rate. When the recording rate is set to at least about twice the transmission rate for inputting the digitized video signal or audio signal, therefore, the recording of an input signal to a medium and the video/audio reproduction from the signal read from an arbitrary point on the medium can be carried out at the same time.